Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip...

Stress-shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high-demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)-assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n = 21) versus noncemented (n = 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press-fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (-45 to -53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (-11 to -20%). Cancellous BD decrased only ventral (-21 to -31%) and in two scans cranial (-11 and -12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press-fit component. Long-term results are required to prove whether third-generation cementing technique protects periprosthetic BD and thereby improve implant survival.